1. Field of Invention
The present disclosure relates to tomography and, more particularly, to a dimensional reference for use in tomography that is capable of providing length scales in three dimensions.
2. Description of Related Art
Tomography may be used to obtain images of human tissue by section. The image may be obtained through modalities such as X-ray computed tomography or magnetic resonance imaging (MRI) tomography. The modality for X-ray computed tomography (X-ray CT) includes medical computed tomography (medical CT) as well as micro computed tomography (micro-CT). Micro-CT is a term that may be used to describe CT systems having a resolution on the order of one micrometer to one hundred micrometers. Nodules and lesions are examples of human tissue that may be imaged using tomography. Because such nodules and lesions may be cancerous, it may be desirable for medical personnel to monitor any such nodule or lesion in order to determine an appropriate treatment protocol. One indicator that may point to cancer is a change in the size of the nodule or lesion.
Changes in the size of a nodule or lesion may be difficult to determine due to different measurement protocols. Accordingly, physicians may need to determine whether an apparent change in nodule or lesion size that is seen on a subsequent patient visit is an actual change, or whether the apparent change in size is due to a measurement error.
Measurement errors that result in apparent changes in nodule or lesion sizes may be caused by a number of factors. For example, where a patient has one hospital perform a first measurement, and then a second hospital perform a subsequent measurement, measurement differences may occur simply because different measurement protocols are used. Moreover, operators for imaging instruments may have different measurement protocols. In addition, factors such as different scan protocols, changes in hardware and software used in the measurement process, as well as changes in imaging instruments may cause an apparent change in nodule or lesion size.
Measurement errors may have a grave effect in that an apparent change, e.g., an increase, in nodule or lesion size may lead to a false positive diagnosis. On the other hand, where the true size of the nodule or lesion is masked, a false negative diagnosis may result.
Various fiducial reference apparatuses have been deployed to monitor a nodule's size. These fiducial reference apparatuses are sometimes known as phantoms. However, these apparatuses may be very expensive, often costing thousands of dollars.
There is a need for dimensional reference apparatus that can significantly reduce measurement errors, and that has a reasonable cost.